1. Field of the Invention
The embodiments of the invention generally relate to computer-implemented decision support systems for determining production planning. General methodologies within this field of study include advanced planning systems, optimization and heuristic based algorithms, constraint based programming, and simulation. More particularly, the embodiments of the invention relate to a production planning method that avoids or limits early builds.
2. Description of the Related Art
A fundamental problem faced in all manufacturing industries is the allocation of material and capacity assets to meet end customer demand. Production lead times necessitate the advance planning of production starts, interplant shipments, and material substitutions throughout the supply chain so that these decisions are coordinated with the end customers' demand for any of a wide range of finished products (typically on the order of thousands in semiconductor manufacturing). Such advance planning depends upon the availability of finite resources which include: finished goods inventory, work in process inventory (WIP) at various stages of the manufacturing system, and work-center capacity. Often, there are alternative possibilities for satisfying the demand. Products may be built at alternative locations and within a location there may be choices as to which materials or capacity to use to build the product. The product may be built directly or acquired through material substitution or purchase. When limited resources prevent the satisfaction of all demands, decisions need to be made as to which demands to satisfy and how to satisfy them. This resource allocation problem is often addressed through linear programming.
A linear program (LP) is composed of an objective function that defines a measure of the quality of a given solution, and a set of linear constraints. A production planning linear program (such as described in U.S. Pat. No. 5,971,585, Dangat, et al., “Best can do matching of assets with demand in microelectronics manufacturing,” Oct. 16, 1999, and incorporated herein by reference) will determine production planning decisions including: manufacturing releases, material substitutions, and shipments planned to customers, between manufacturing and distribution locations, and from vendor suppliers. Similar production planning methods are also disclosed in the following reference (incorporated herein by reference): U.S. Pat. No. 5,943,484, Milne, et al., “Advanced material requirements planning in microelectronics manufacturing,” Aug. 24, 1999. However, while these prior art references disclose planning methods that were satisfactory for the purposes for which they were intended, there is still a need in the art for computer-implemented production planning methods that provide improvements over the prior art.